Chemistry and Physies. 415 
advantages of having a reservoir of electricity, however, compen- 
sate ven ag loss of energy.— Comptes Rendus, March 6, sek 
ae J. 
ab aye of Electricity. Professor Ayrton, F.R.S., deli abut 
a Gece on the storage of energy at the London Institution, 
March 2,in which he maintains, allowing for the unnecessary 
waste due to the too hurried charging and too hurried discharg- 
g a Faure accumulator, “that for a million foot-pounds of 
stored energy discharged with a mean current of 17 ampéres, the 
loss in charging = discharging combined need not exceed 18 
per cent,” and in some cases he has found it not to exceed 10 per 
cent. He has f fond fren experiment that 81 pounds of lead and 
red lead charged and discharged, the discharge lasting eighteen 
hours—six -hours on three successive days—represented in its 
discharge 1,440,000 foot pounds of work, or I-horse power for 
three-quarters 0 of an hour. 
The resuscit: ee power of the Faure accumulator was wonder- 
ful. After t ae bers of discharge just referred to it was 
found after a fi Sat s of insulation that the eisin ulaeer could 
give a current of over ae annpeeek The phenomenon resembles 
0 : 
15. i as Sound i" Wood ; by Dr. H. nena) (Com. 
in regard to it, erm at a somewhat late date. Mr. Ihlseng 
defines the velocity of sound in wood in two ways: in the first, 
the rod of wood is fixed in the middle, one end is rubbed and the 
other end marks its vibrations on a blackened glass plate; by 
ck means are found the number of scat n, and half the 
wave length in wood, 3? equal to the length of the rod; then the 
velocity is »=nA, The number of vibrations can also be found 
by Kundt’s method, the bing of the rod causing the air in a tube 
to vibrate; if = designates half the wave length of air in the 
: : a 
tube, a the velocity of sound in the tube, then n=, and there- 
fore age © 
Mr. Ihlseng se pie in every case greater velocities by the 
second method than by the first, and was unable to fin d Bs 
reason for the iasuse I think the explanation is easily given, 
and it is this which induces me to send this note. Unfortunately 
Mr. Ihlseng gives the results of his researches so very incom- 
pletely, that I cannot be sure that my supposition is cael but 
from the words of the a uthor, I must Presume, that ca gata. 
m 
in free air, that is to say about 3925-2", This would be allowa- 
